1. Field of the Invention
The invention relates to a split cage for a rolling bearing, in which a plurality of cage segments is arranged in a circular manner, and relates also to a rolling bearing using the split cage.
2. Description of Related Art
Conventionally, in a horizontal axis propeller-driven wind power generator, a rolling bearing is used so that a main shaft to which blades are attached is rotatably supported. In recent years, wind power generators have become larger, and accordingly the diameter of a main shaft of a wind power generator may be several meters or more. Accordingly, rolling bearings have become larger in order to support such a large-sized main shaft. As a cage for a large-sized rolling bearing, a cage made of a synthetic resin may be used. The synthetic resin cage has the advantages, over a metal cage assembled by welding, that the synthetic resin cage is light and sufficient accuracy of the synthetic resin cage is easily achieved. However, it is difficult to form the synthetic resin cage with a large diameter, as a single-piece member, by injection molding. Therefore, a split cage that is formed of a plurality of pieces arranged in the circumferential direction is used (see, for example, EP Patent No. 2264325 (A1)). The split cage has a plurality of cage segments arranged in a circular manner.
FIG. 8 is a perspective view of main portions of an example of a conventional cage segment. The cage segment 100 has a pair of first and second rims 101, 102, and a plurality of cage bars 103. The first rim 101 and the second rim 102 face each other while being separated from each other by a predetermined distance. The cage bars 103 extend from the first rim 101 to the second rim 102. In the cage segment 100, pockets 104 that accommodate tapered rollers (not shown), which serve as rolling elements, are formed of spaces each of which is defined by the two cage bars 103 adjacent to each other, the first rim 101, and the second rim 102. The cage segment 100 is made of a synthetic resin and formed by injection molding.
An outer guide portion 114 is formed on the outer periphery of each of the cage bars 103 so as to project from the outer periphery. The outer guide portions 114 are in sliding contact with an outer ring raceway surface of a rolling bearing to guide the rotation of the cage segment 100. A pair of inner guide portions 115 is formed on the inner periphery of each of the cage bars 103 so as to project from the inner periphery. The inner guide portions 115 in each pair are apart from each other in the axial direction. The inner guide portions 115 are in sliding contact with an inner ring raceway surface of the rolling bearing to guide the rotation of the cage segment 100. Among the inner guide portions 115, the inner guide portions 115 on the second rim 102 side also serve as holding portions that hold the tapered rollers from the radially inner side.
In the conventional split cage, one of the cage segments 100 adjacent to each other may be pressed in the circumferential direction by the other one of the adjacent cage segments 100, for example, if the rolling speed of the tapered rollers 113 in the one of the adjacent cage segments 100 falls below that of the tapered rollers 113 in the other one of the adjacent cage segments 100, or if thermal expansion of each of the cage segments 100 occurs. In this case, because end faces of the rims 101, 102 of the one of the adjacent cage segments 100 and end faces of the rims 101, 102 of the other one of the adjacent cage segments 100 press each other, radial sliding may occur between the end faces of the one of the adjacent cage segments 100 and the end faces of the other one of the adjacent cage segments 100. As a result, the adjacent cage segments 100 may be displaced relative to each other in the radial direction. If such a displacement of the adjacent cage segments 100 occurs, the outer peripheries of the outer guide portions 114 of the one of the adjacent cage segments 100 come into sliding contact with the outer ring raceway surface while being strongly pressed against the outer ring raceway surface. The inner peripheries of the inner guide portions 115 of the other one of the adjacent cage segments 100 come into sliding contact with the inner ring raceway surface while being strongly pressed against the inner ring raceway surface. Therefore, the outer guide portions 114 and the inner guide portions 115 may wear abnormally. As a result, the cage segments 100 may vibrate in the radial direction or the performance of the rolling bearing may be adversely affected by wear debris.